Hi Jóhann,
Can you confirm that your road features are represented as lines- not as polygons?
Almost all represent roads as lines ( the line width can be specified for each line).
There are two ways to add elevation values to the road segments:
1) either use an existing Digital elevation Model (DEM) as source of elevation values
that will be used to add elevation values to the rasterized line.
The DEM cell size may need to be at most equal to the width of the road,
say for a 7-meter wide road (3.5 meter wide lane with 1 lane per direction), you'd need a DEM with at most a 7-metre cell size, the smaller cellsize the better.
The road line will need to be converted to a raster image.
The image cell size should be close in value to the road width.
You can perform a raster operation on both rasters so that all cells representing the road line in the rasterized image will inherit the elevation of the nearest cell from the DEM image.
This way the road will have elevations every pixel width.
2) to perform actual fieldwork and acquire GPS readings of the coordinates (Easting, northing and elevation) of the roads. But this is less representative of the actual undulating profile of the road
I hope this helps!
